(a) Field of the Invention
The present invention relates to a method for manufacturing an LCD (liquid crystal display) device and, more particularly, to a method for manufacturing an LCD device having therein an aluminum (Al) or Al-alloy film pattern which constitutes metallic lines and electrodes.
(b) Description of the Related Art
An LCD device having thin-film transistors (TFT) as switching devices generally suffers from a problem in the operational speed thereof and a cross-talk problem if the scanning lines or signal lines involve a larger propagation delay. In particular, a large-size high-definition LCD device uses a low-resistivity substance for the material of the scanning lines and signal lines for avoiding such a problem. Although Al or Al alloy is widely used as the low-resistivity substance for implementing the metallic lines, Al or Al alloy is generally combined with a high-melting-point metal (HMPM) to form multilayer metallic lines. Such an multilayer metallic line may have a two-layer metallic structure, such as HMPM film (top layer)/Al film (bottom layer), or three-layer metallic structure, such as HMPM film/Al film/HMPM film, thereby assuring a suitable ohmic contact with a semiconductor layer and/or a transparent conductive layer.
The multilayer metallic line having the above two-layer or three-layer metallic structure may be patterned using a single photolithographic and etching step for the purpose of reducing the number of photolithographic and etching steps and thus reducing the fabrication costs. In this case, Al or Al-alloy film (simply referred to as Al film collectively, hereinafter) appears on the side walls of the resultant metallic line.
In fabrication of a TFT panel of a reverse-staggered type having the three-layer metallic structure in the signal lines, a dray etching process is generally used for configuring the channel region of the TFT and patterning the semiconductor layers. The dry etching generally uses fluorine-based gas such as SF6 and CHF3, chlorine-based gas such as Cl2 and HCl, or a mixture of these gases. If Al or Al-alloy is exposed from the side walls of the signal lines, as described above in connection with the single photolithographic and etching step, there occurs a problem in that Al in the exposed Al film is corroded by the etching gas during the dry etching. This is considered due to the fact that Al reacts with fluorine-based gas or chlorine-based gas to generate Al fluoride or Al chloride, or that Al reacts with water in the atmosphere to generate hydrofluoric acid or hydrochloric acid, after the TFT panel onto which residual fluorine-based gas or chlorine-based gas is attached is taken out in the atmosphere after the dry etching, the fluoride or acid corroding the Al film. Thus, a method is desired which is capable of manufacturing an LCD device while preventing the Al corrosion.
Patent Publication JP-A-1996-62628 describes a technique for preventing the Al corrosion, wherein an oxide film is formed on the interface between the Al film and the HMPM film and on the side walls of the Al film used as source/drain electrodes and signal lines in an LCD device, thereby preventing the bimetallic local corrosion which may occur during the step of removing resist etc. by peel-off. It is recited in the publication that the side-wall oxide film for the Al film can be formed by plasma oxidation, anodic oxidation, CVD or plasma-enhanced CVD (PVD).
The technique described in the above publication increases the number of fabrication steps by addition of the oxidation or CVD step. In addition, it is difficult to obtain a sufficient thickness of the oxide film by using the plasma oxidation step with a reasonable time length: an oxide film having a small thickness around several nanometers, for example, cannot effectively prevent the Al corrosion caused by the etching gas during the dry etching. The anodic oxidation may provide a sufficient thickness for the oxide film; however, the anodic oxidation limits the choice of the high-melting-point metals allowing the anodic oxidation. For example, Mo is inadequate to the anodic corrosion, as recited in Patent Publication JP-A-1988-276242. The CVD or PVD process may include at least an additional etch-back step for the deposited oxide film to thereby complicate the fabrication process.
In view of the above problems in the conventional technique, it is an object of the present invention to provide a method for manufacturing an LCD device, including the process for forming a layer structure including Al film and an HMPM film substantially without complicating the process and yet capable of preventing the Al corrosion.
The present invention provides, in a first aspect thereof, a method for manufacturing a liquid crystal display (LCD) device including: consecutively forming a semiconductor layer and a multilayer metallic film to overlie a substrate, the multilayer metallic film including a high-melting-point metal (HMPM) film and a first metallic film having a lower resistivity than the HMPM film; forming a photoresist mask on the multilayer metallic film; patterning the multilayer metallic film by using the photoresist mask to form a multilayer metallic pattern, the patterning including a side etching for retracting edges of the multilayer metallic pattern beyond edges of line patterns of the photoresist mask; forming a protection film on exposed portions of the first metallic film; dry-etching at least a portion of the semiconductor layer by using the photoresist mask as an etching mask; and removing the photoresist mask.
The present invention provides, in a second aspect thereof, a method for manufacturing a liquid crystal display (LCD) device including: consecutively forming a semiconductor layer and a multilayer metallic film to overlie a substrate, the multilayer metallic film including a high-melting-point metal (HMPM) film and a first metallic film having a lower resistivity than the HMPM film; forming a photoresist mask on the multilayer metallic film; patterning the multilayer metallic film by using the photoresist mask to form a multilayer metallic pattern, the patterning including a side etching for retracting edges of the multilayer metallic pattern beyond edges of line patterns of the photoresist mask; removing the photoresist pattern; forming a protection film on exposed portions of the first metallic film; and dry-etching at least a portion of the semiconductor layer by using the photoresist mask as an etching mask.
The present invention provides, in a third aspect thereof, a. method for manufacturing a liquid crystal display (LCD) device including: consecutively forming a semiconductor layer and a multilayer metallic film to overlie a substrate, the multilayer metallic film including a high-melting-point metal (HMPM) film and a first metallic film having a lower resistivity than the HMPM film; forming a photoresist mask on the multilayer metallic film; patterning the multilayer metallic film by using the photoresist mask to form a multilayer metallic pattern; dry-etching at least a portion of the semiconductor layer by using the photoresist mask and/or the multilayer metallic pattern as an etching mask; and evacuating a chamber upon completion of the dry-etching step in the chamber to remove etching gas used in the dry-etching step from the substrate including the multilayer metallic pattern.
The present invention provides, in a fourth aspect thereof, a method for manufacturing a liquid crystal display (LCD) device including: consecutively forming a semiconductor layer and a multilayer metallic film to overlie a substrate, the multilayer metallic film including a high-melting-point metal (HMPM) film and a first metallic film having a lower resistivity than the HMPM film; forming a photoresist mask on the multilayer metallic film; patterning the multilayer metallic film by using the photoresist mask to form a multilayer metallic pattern; dry-etching at least a portion of the semiconductor layer by using the photoresist mask as an etching mask; and removing the photoresist mask by using a wet peel-off process and simultaneously washing the substrate including the multilayer metallic pattern within a time length of 10 minutes after completion of the dry-etching step.
The present invention provides, in a fifth aspect thereof, a method for manufacturing a liquid crystal display (LCD) device including: consecutively forming a semiconductor layer and a multilayer metallic film to overlie a substrate, the multilayer metallic film including a high-melting-point metal (HMPM) film and a first metallic film having a lower resistivity than the HMPM film; forming a photoresist mask on the multilayer metallic film; patterning the multilayer metallic film by using the photoresist mask to form a multilayer metallic pattern; removing the photoresist mask; dry-etching at least a portion of the semiconductor layer by using the multilayer metallic pattern as an etching mask; water-washing the substrate including the multilayer metallic pattern within a time length of 10 minutes after completion of the dry-etching step.
In accordance with the methods of the present invention, the corrosion of a metal in the first metallic film due to the etching gas used in the dry etching can be suppressed by respective configurations of the methods of the present invention.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.